The present invention relates to the illumination arts, lighting arts, solid state lighting arts, electronics arts, thermal management arts, and related arts.
Solid state lighting presents substantial thermal management issues due to the heat sensitivity and low optimal operating temperature of many solid state lighting devices, combined with low radiative and convective cooling efficiency due to the low optimal operating temperature. For example, light emitting diode (LED) devices typically have an optimal operating temperature of about 100° C. or lower, at which temperatures radiative and convective heat transfer away from the LED devices is inefficient.
Passive cooling solutions relying upon a large heat sink in thermal communication with the solid state lighting devices is of limited effectiveness. Active cooling can be more effective. For example, synthetic jets have been employed for cooling in solid state lighting. See, e.g., Arik et al., U.S. Pub. No. 2004/0190305 A1, which is herein incorporated in its entirety by reference; Bohler et al., Int'l. Appl. No. WO 2004/100213 A2, which is herein incorporated in its entirety by reference. Synthetic jets have also been employed in other cooling applications such as cooling of electronic modules. However, synthetic jets or other active cooling (e.g., fan based cooling, see e.g. Cao, U.S. Pat. No. 6,465,961) have substantial disadvantages in solid state lighting applications. The active cooling system occupies valuable space, which is especially problematic in compact lighting units and/or self contained lighting units such as retrofit lamps or light bulbs in which the electronics for driving the solid state lighting devices off of wall voltage (e.g., 110V a.c. or 220V a.c.) are integrated into the lighting unit. Positioning of the active cooling sub system in a way that is sufficiently proximate to the solid state lighting devices in order to provide cooling while not blocking the optical path is also problematic.